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Table 3 Susceptibility of P. aeruginosa biofilms to various treatments after 3 and 60 days of growth, determined by disk diffusion

From: Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms

MaterialDose on disk (μg)ZOI (mm)
day 3
ZOI (mm)
day 60
Fe3O4 NPs1022/S21/S
517.5/S16/S
2.511/R10/R
Fe3O4@PEG NPs100/R0/R
50/R0/R
2.50/R0/R
Fe3O4@ALG NPs1022/S22/S
516/S15/S
2.510/R8/R
Fe3O4@ALG:TOBRA NPs1023/S22/S
511/R15/I
2.57/R5/R
ZVFe@ALG NPs1025/S24/S
521/S22/S
2.520/S20/S
Tobramycin10*10/R0/R
100**25/R**15/R**
1000**35/R**32/R**
  1. Interpretation: R resistant, I bintermediate, S susceptible, ZOI zone of inhibition, PEG polyethylene glycol, ALG alginate, TOBRA tobramycin, ZVFe zero-valent iron
  2. Uncapped NPs. *CLSI breakpoint for susceptibility of tobramycin by disk diffusion is 10 μg. Therefore, all colonies are found to be tobramycin resistant by CLSI standards. **Higher tobramycin doses in the disk were investigated to determine whether any susceptibility existed at higher doses. At present, there are no CLSI values/breakpoints for NPs as antimicrobial agents